1. Field of the Invention
The present invention relates to a method of diamond nucleation and a structure formed thereof. More particularly, the present invention relates to a method of graphene induced diamond nucleation and a structure formed thereof.
2. Description of Related Art
Diamond has excellent physical, chemical, optical, mechanical, and electrical properties. For example, diamond has high thermal conductivity coefficient, chemical inertness, highest rigidity, high Young's modulus, low friction coefficient, wide energy gap, and broad optical transmission frequency-domain. As a result, polycrystalline diamond (PCD) has been widely used in industry in recent years. Polycrystalline diamond not only has excellent mechanical property similar to monocrystalline diamond, but can also be processed into any desired shape according to different purposes.
When forming diamonds on non-diamond substrates, seeding or nucleation of diamond on non-diamond substrates must be done first. Since self-nucleation without needing to place diamond particles on a substrate simplifies diamond deposition processes, there are many studies dedicated to methods of diamond self-nucleation. One kind of heterogeneous nucleation is bias-enhanced nucleation (BEN). During bias-enhanced nucleation, a negative bias voltage with respect to the plasma is applied externally on substrates. Kinetic energy of species is then increased, collision of species to substrates is increased, and nucleation is enhanced. However, uniform biasing of large areas and high flux of bias induced ion bombardment on highly-resistive substrates are more difficult during bias-enhanced diamond nucleation processes. Bias-enhanced diamond nucleation also fails to penetrate into narrow grooves in substrates in order to enhance diamond nucleation on the sidewalls of grooves where the electric field perpendicular to the sidewall surface is weak. Although some related researches have reported that additional coating layers, such as an amorphous carbon layer, can also promote nucleation. However, the nuclei formed usually are of low density and fail to distribute evenly.
Nowadays, chemical vapor deposition (CVD) is a common and well-developed method for polycrystalline diamond film formation. The precursors used are usually hydrocarbon materials, or carbon-containing materials with addition of different amounts of argon gas, hydrogen gas, oxygen gas, and nitrogen gas, etc. The polycrystalline diamond film is formed by ionizing, exciting, and decomposing gas mixtures containing the aforesaid precursors using various types of energy sources. In particular, in microwave plasma chemical vapor deposition (MPCVD), one or more reactive materials provided into reactors are first activated by microwave plasma. Ionization, decomposition, recombination, and chemical reactions of the reactive materials then occur. A solid film is then deposited on a diamond surface or a surface of non-diamond substrates having diamond nuclei. However, until now, it is still rather difficult to deposit a diamond film on substrates without diamond seeding and without negative biasing voltage using microwave plasma chemical vapor deposition.
Therefore, there is a need to develop a method of diamond nucleation without the need to perform diamond seeding or to externally apply negative bias voltage on non-diamond substrates. In addition, there is also a need to develop a method of diamond nucleation that can improve uneven distribution and penetration into grooves of substrates of diamond nuclei formed by the use of additional coating layers.